Aluminum-based Water Treatment Residuals Research Articles

Green engineered mulch for phosphorus and metal removal from stormwater runoff in bioretention systems

Phosphorus and metals in stormwater runoff are major causes of water quality degradation. Bioretention systems are increasingly implemented to improve stormwater quality and to better manage stormwater quantity. Many studies have focused on modifying the composition of the soil bed to improve pollutant removal. However, the pollutant removal performance of bioretention systems can diminish over time, such as when clogging of the media occurs. Sediment accumulation on the soil surface may inhibit infiltration into the soil bed, thus limiting pollutant removal. Soil replacement may be eventually required as pollutants accumulate in the soil. In this study, a green retrofit material, called green engineered mulch (GEM), was generated by coating regular wood mulch with aluminum-based water treatment residuals (WTR) via a simple and low-energy process (patent pending). The GEM was developed to serve as a green retrofit for bioretention systems to enhance the removal of phosphorus and metals from stormwater runoff. The GEM was placed in a rain garden in Secaucus, NJ, USA for 15 months, during which 12 storm events (ranging from 6.0 mm to 89.6 mm) were monitored. Runoff and infiltrate samples were analyzed for dissolved and total concentrations of phosphorus and metals, along with other key water quality parameters. The GEM significantly reduced (p < 0.05) the total concentrations of phosphorus and metals in stormwater infiltrate compared to the inlet, unlike the regular mulch. Minimal or no contact with the GEM resulted in no significant pollutant removal from surface runoff. No significant pollutant export from the GEM was observed. The spent GEM can be disposed of as non-hazardous waste in municipal landfills. This study demonstrates that the GEM is a safe and effective retrofit. Moreover, the GEM is a simple and economical retrofit solution that can be used in place of regular mulch in bioretention systems.

Correlation of Phosphorus Adsorption with Chemical Properties of Aluminum-Based Drinking Water Treatment Residuals Collected from Various Parts of the United States.

Over the past several decades, the value of drinking water treatment residuals (WTRs), a byproduct of the coagulation process during water purification, has been recognized in various environmental applications, including sustainable remediation of phosphorus (P)-enriched soils. Aluminum-based WTRs (Al-WTRs) are suitable adsorbent materials for P, which can be obtained and processed inexpensively. However, given their heterogeneous nature, it is essential to identify an easily analyzable chemical property that can predict the capability of Al-WTRs to bind P before soil amendment. To address this issue, thirteen Al-WTRs were collected from various geographical locations around the United States. The non-hazardous nature of the Al-WTRs was ascertained first. Then, their P adsorption capacities were determined, and the chemical properties likely to influence their adsorption capacities were examined. Statistical models were built to identify a single property to best predict the P adsorption capacity of the Al-WTRs. Results show that all investigated Al-WTRs are safe for environmental applications, and oxalate-extractable aluminum is a significant indicator of the P adsorption capacity of Al-WTRs (p-value = 0.0002, R2 = 0.7). This study is the first to report a simple chemical test that can be easily applied to predict the efficacy of Al-WTRs in binding P before their broadscale land application.

Adsorption of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) by aluminum-based drinking water treatment residuals

Per- and polyfluoroalkyl substances (PFAS) represent a family of emerging persistent organic pollutants. Cost-effective remediation of PFAS contamination via chemical or biochemical degradation is challenging due to their extremely high stability. This study reports the removal of two representative PFAS species, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), from water by adsorption using aluminum-based water treatment residuals (Al-WTR), a non-hazardous waste generated during the process of drinking water treatment by alum salts. Rapid adsorption of PFOA and PFOS onto Al-WTR followed a pseudo 2nd order kinetic pattern. Lower pH facilitated the adsorption process with a faster adsorption rate and greater adsorption capacity. At pH 3.0 and an initial concentration of 1.0 mg/L, 97.4 % of PFOA and 99.5 % of PFOS were adsorbed onto Al-WTR. Adsorption isotherm modeling showed that the maximum adsorption capacities of PFOA and PFOS on Al-WTR at pH 3.0 were 0.232 and 0.316 mg/g, respectively. Desorption tests indicated that the adsorption by Al-WTR was irreversible, making Al-WTR an excellent candidate for treating PFOA and PFOS in solution. The highly encouraging results of this preliminary study indicate that Al-WTR may be a promising, viable, and cost-effective PFOA/PFOS treatment option for water reuse, industrial wastewater treatment, and groundwater remediation.

Phosphorus removal from swine wastewater using aluminum-based water treatment residuals

Abstract Aluminum water treatment residuals (Al-WTR), a waste product created during drinking water treatment, is generated in large quantities globally and typically landfilled; alternative, uses are desperately required. Inorganic phosphorus (P) is proven to be quickly and irreversibly sorbed by Al-WTR, rendering P unavailable for subsequent environmental use. However, little work has been done to characterize how Al-WTR interacts with organic P sources (e.g., wastewaters) to both sorb and later release P. Experiments characterized Al-WTR's ability sorb and subsequently desorb swine wastewater organic P, and to ascertain Al-WTR's potential for agricultural wastewater treatment and to return organic P to systems (e.g., soils) for beneficial use. Al-WTRs were shaken with swine wastewater (2.5:1;w/w) and solution total/inorganic/organic P were monitored over 21 days. The Al-WTR sorbed almost 100% (~ 16,500 mg kg−1) of swine wastewater organic P within a 1-h timeframe. X-ray absorption near-edge spectroscopy showed that P was primarily sorbed by Ca phases present in Al-WTR during the initial 1-h sorption phase. In a subsequent study, the newly generated organic P-laden Al-WTR was shaken in 0.01M KCl along with an anion membrane-probe to capture desorbed P. Approximately 17% (~ 3000 mg kg−1) of the organic P sorbed onto Al-WTR was desorbed. Findings suggest that Al-WTR can remove excessive organic P from agricultural waste streams, with the Al-WTR-organic P-containing material potentially having the ability to supplement agricultural soils with P for plant use. By following such an approach, this could provide municipalities with an alternative and beneficial utilization strategy as compared to landfilling.

Making Phosphorus Fertilizer from Dairy Wastewater with Aluminum Water Treatment Residuals

Core Ideas Al‐WTR sorbed P from dairy wastewater and subsequently applied as fertilizer to lettuce. The Al‐WTR acted as a P source, increasing lettuce yield and plant P concentrations. Al‐based WTR loaded with P can compete successfully with common fertilizers. Phosphorus recovery and recycling can improve the sustainability of nutrient use in agriculture. In this study, P was recovered by reacting aluminum‐based water treatment residuals (Al‐WTR) with organic matter‐rich, high P concentration (60–100 mg L–1) dairy wastewater. The resulting P‐rich (500–700 mg kg–1 Olsen P, ∼10 g kg–1 total P) Al/O‐WTR was applied as fertilizer in screen houses using romaine lettuce (Lactuca sativa L. var. longifolial) planted in Typic Haploxerolls with limited bioavailable P (&lt;10 mg kg–1). Two experiments were conducted in 10‐L pots: (i) fertilizer comparison, with liquid fertilizer (N, P, K, and micronutrients), slow release fertilizer (N, P, K, and micronutrients), liquid fertilizer with no P (control), and liquid fertilizer with ∼5 g Al/O‐WTR per kg soil (∼15 t Al/O‐WTR ha–1); (ii) Al/O‐WTR rate comparison (∼0, 2, 3, 5, and 7 g kg soil–1, equivalent to 0, 6, 10, 15, and 22 t Al/O‐WTR ha–1). In the fertilizer comparison, lettuce biomass was significantly greater in all treatments (&gt;140 g pot–1) compared to the control (57 g pot–1). In the rate comparison experiment, lettuce biomass was also significantly greater in the Al/O‐WTR treatments (412 to 512 g pot–1) compared to the control (309 g pot–1). The highest additions of Al/O‐WTR produced the highest lettuce yield. Lettuce yield and P concentration were similar across treatments, indicating that Al/O‐WTR can provide sufficient P to perform similarly to common fertilizers. Recovery and reuse of P using Al‐WTR may therefore improve the sustainability of nutrient cycling in agriculture.

Phosphorus Sorption on Aluminum‐based Water Treatment Residuals

CSA NewsVolume 63, Issue 8 p. 12-12 Society Science Phosphorus Sorption on Aluminum-based Water Treatment Residuals First published: 02 August 2018 https://doi.org/10.2134/csa2018.63.0812Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume63, Issue8August 2018Pages 12-12 RelatedInformation

Phosphorus Removal in Constructed Stormwater Wetland Mesocosms Amended with Water Treatment Residuals.

Constructed stormwater wetlands (CSWs) reduce stormwater volume and improve water quality. One quality improvement is the removal of soluble reactive phosphorus (SRP). There has been limited study on SRP fate and transport or on the mechanisms to improve SRP removal due to the difficulty in quantifying the complex, spatially heterogeneous removal processes in two-dimensional flow. The present research analyzed the ability of wetland soil (Control) and wetland soil amended with 2%, 5%, and 8% (by mass) of aluminum-based water treatment residuals (AlWTRs) to remove SRP in surface-flow vegetated CSW mesocosms. Batch adsorption experiments showed increasing SRP sorption capacity with increased AlWTR content (590-850 mg/kg soil) compared to the Control (385 mg/kg soil); however, AlWTR-amended flowing mesocosms removed only 6.0-8.8 mg/kg SRP compared to 9.3 mg/kg SRP for the Control. The lack of increased SRP removal in AlWTR-amended mesocosms was attributed to flow dynamics (only 20% of the surface outflow was quantified as subsurface flow). These results suggest the extent of infiltration versus surface flow is key to soil amendments improving SRP removal in a CSW.

Coagulation/flocculation process for dye removal using water treatment residuals: modelling through artificial neural networks

AbstractThe potential of aluminum-based water treatment residuals (WTR) discharged from water treatment plants was evaluated as a coagulant for color removal from a disperse dye solution. The effects of WTR dose, initial dye concentration, and initial pH on color removal were studied. The results showed higher color removal at lower pH values. Maximum color removals of 88, 87, and 76% were obtained for initial dye concentrations of 25, 50, and 75 mg/L, respectively, at pH 3.0 with a WTR dose of 3,000 mg/L. Different artificial neural networks (ANN) were developed for predicting the color removal. The performance of the models was found to be very good, with correlation coefficient (R2) values greater than 0.90. The results showed that simulation employing ANN incorporates non-linear behavior of the system, and the model-predicted and observed values of color removals were in close agreement with each other. The study thus indicates that reusing water treatment sludge as a coagulant for color removal would...

Insights into the mechanisms of mercury sorption onto aluminum based drinking water treatment residuals

Several studies have demonstrated the ability of drinking water treatment residuals (WTRs) to efficiently sorb metal cations from aqueous solutions. Reported results have stimulated interest on the potential use of WTRs as sorbent for metal removal from contaminated aqueous effluents as well as in metal immobilization in contaminated soils. However, knowledge on mechanisms of metal sorption by WTRs remains very limited and data on the long-term stability of formed metal–WTR complexes as a function of changing key environmental parameters are lacking. In this study, chemical selective sequential extraction (SSE), scanning electron microscopy combined with X-ray energy dispersive spectrometer (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) were used to gain insight into the different mechanisms of mercury (Hg) binding to aluminum based WTR (Al-WTRs). Results from sorption studies show that a significant portion of Hg becomes incorporated in the operationally defined residual fraction of Al-WTRs, and therefore, not prone to dissolution and mobility. The results of solid phase analyses suggested that Hg immobilization by Al-WTR occurs largely through its binding to oxygen donor atoms of mineral ligands driven by a combination of electrostatic forces and covalent bonding.

Aluminum-Based Water Treatment Residual Use in a Constructed Wetland for Capturing Urban Runoff Phosphorus: Column Study

Aluminum-based water treatment residuals (Al-WTRs) have a strong affinity to sorb P. In a proof- of-concept greenhouse column study, Al-WTR was surface-applied at rates equivalent to 0, 62, 124, and 248 Mg ha −1 to 15 cm of soil on top of 46 cm of sand; Al-WTR rates were estimated to capture 0, 10, 20, and 40 years of P from an urban watershed entering an engineered wetland in Boise, ID, USA. Creeping red fescue (Festuca rubra) was established in all columns; one set of columns received no Al-WTR or plants. After plant establishment, once per week over a 12-week period, ∼1.0 pore volumes of ∼0.20 mg P L −1 were added to each column. Infiltration rates were measured, leachate was collected and analyzed for soluble P, and fescue yield, P concentration, and uptake were deter- mined. After plant harvest, the sand, soil, and the Al- WTR layer were collected and analyzed for Olsen P; amorphous Al, Fe, and P; P storage capacity (PSC); and soluble + Al + Fe-bound, occluded, and Ca-bound P phases. Infiltration rate increased only due to the pres- ence of plants. Leached P decreased (50 %) with plants present; Al-WTR further reduced soluble P leaching losses (60 %). Fescue yield, P concentration, and uptake increased with increasing Al-WTR rate, due to Al-WTR sorbing and potentially making P more plant available; Olsen-extractable P increased with increasing Al-WTR rate, supporting this contention. The PSC was reduced with the 62 Mg ha −1 Al-WTR rate but maintained with greater Al-WTR rates. The 124 and 248 Mg ha −1 Al- WTR rates also contained greater P associated with the soluble + Al + Fe and occluded phases which should be stable over the long term (e.g., decadal). It was recom- mended to apply Al-WTR near the 124 and 248 Mg ha −1 rates in the future to capture urban runoff soluble P in the Boise, ID, engineered wetland.

Nitrate and Phosphate Removal through Enhanced Bioretention Media: Mesocosm Study

Bioretention is an evolving type of Green Stormwater Infrastructure (GSI) designed to attenuate peak flows, reduce stormwater volume, and treat stormwater. This article examines the capabilities of a bioretention soil mixture of sand and compost enhanced with aluminum-based drinking water treatment residuals to reduce nutrients from stormwater runoff. Columns with and without a saturation zone and vegetation were compared to examine their role in removing nitrate and ortho-phosphate from stormwater. Results show that utilization of a saturation zone can significantly reduce nitrate in effluent water (71% compared to 33% without a saturated zone), even in a newly constructed system. However, ortho-phosphate reduction was significantly better in the columns without a saturated zone (80%) compared to columns with (67%). Plants did not significantly improve removal. This suggests amendments such as aluminum-based water treatment residuals for phosphorus removal and a saturation zone for nitrogen removal are needed during the initial establishment period.

Removal of boron using aluminum-based water treatment residuals (Al-WTRs)

Three samples of aluminum-based water treatment residuals (Al-WTR1, Al-WTR2, and Al-WTR3) were assessed as adsorbent for boron removal. The Al-WTRs were mainly composed of Al2O3, Fe2O3, and SiO2. The adsorption reaction could be approximated by a pseudo-second-order kinetic model. The equilibrium pH (pHe) affected boron adsorption and the optimum pHe was found at 8.2–8.5. The Langmuir model described the adsorption data satisfactorily (R2 value average ≧ 0.990), and the batch maximum adsorption capacities were found as 0.980, 0.700, and 0.190mg/g using three samples, respectively, at pH value of 8.3±0.2. Thermodynamic analysis revealed that the adsorption reaction was spontaneous and exothermic. The ΔHo value was low (−1.58kJ/mol), and that was indicative of a physical adsorption. Electrostatic interactions and van der Waals force were proposed as major driving forces of adsorption under different pH conditions. Both BET specific surface area and aluminum content of Al-WTRs affected boron adsorption, as judged by the fact that Al-WTR1 showed higher adsorption density than the other two. The results of this study show that Al-WTRs can be used as an alternative adsorbent for boron removal.

Selenium adsorption to aluminum-based water treatment residuals

Aluminum-based water treatment residuals (WTR) can adsorb water- and soil-borne P, As(V), As(III), and perchlorate, and may be able to adsorb excess environmental selenium. WTR, clay minerals, and amorphous aluminum hydroxide were shaken for 24 h in selenate or selenite solutions at pH values of 5–9, and then analyzed for selenium content. Selenate and selenite adsorption edges were unaffected across the pH range studied. Selenate adsorbed on to WTR, reference mineral phases, and amorphous aluminum hydroxide occurred as outer sphere complexes (relatively loosely bound), while selenite adsorption was identified as inner-sphere complexation (relatively tightly bound). Selenite sorption to WTR in an anoxic environment reduced Se(IV) to Se(0), and oxidation of Se(0) or Se(IV) appeared irreversible once sorbed to WTR. Al-based WTR could play a favorable role in sequestering excess Se in affected water sources.